Sensorless Brushless DC Motor Control for Valve Actuation
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Solution Overview
Problem
Existing brushless DC motor control systems rely on position sensors, which are costly and prone to failure, limiting their efficiency and longevity in applications requiring precise torque control and high reduction gear mechanisms, such as ventilation and fire protection systems.
Innovation Solution
The method involves programmatically controlling the electrical current flow in the stator coils without integral position sensors by storing and adapting algorithms in a CPU to detect zero crossings of motor phase voltages, allowing for precise commutation and torque control, and using a pre-tensioned spring mechanism to maintain operation during power failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If position sensors are used to control brushless DC motor commutation, then the motor achieves precise position control and stable operation, but the system cost increases and reliability decreases due to sensor failure risks
Solution Approach 1:
The patent extracts and eliminates the position sensors from the motor control system. Instead of using sensors to detect rotor position, the system uses sensorless control methods including back-EMF detection and current waveform analysis to determine commutation timing, thereby removing the reliability issues and costs associated with physical sensors while maintaining precise control capability
Solution Approach 2:
The motor system performs self-position detection through its own electrical characteristics. The control electronics analyze the motor's back-EMF signals and current consumption patterns to autonomously determine rotor position and commutation timing without external sensing components, enabling the system to serve its own positioning needs
2Measurement precision
If high reduction gear is used to achieve precise flap positioning, then the motor can control large area control elements with weak motors, but the mechanical complexity and potential failure points increase
Solution Approach 1:
The patent replaces the mechanical reduction gear system with an electrical control solution. By using electronic commutation with precisely timed current switching in the stator windings, the system achieves fine positional control of the rotor and connected flap without requiring complex mechanical gear trains, thereby reducing mechanical complexity while maintaining or improving positioning precision
Solution Approach 2:
The system achieves high precision control by dynamically changing electrical parameters including commutation timing, current magnitude, and pulse width modulation duty cycles. These electrical parameter adjustments provide precise torque control and positional accuracy without the need for mechanical reduction mechanisms
3Productivity
If six transistors are used per phase for higher winding utilization, then torque output becomes more even and efficient, but the control system complexity and power loss increase
Solution Approach 1:
The patent implements dynamic control of the power transistor switching sequences and duty cycles. The system continuously adjusts the on/off timing and duration of transistor pairs based on real-time motor load, speed, and position feedback, optimizing the balance between winding utilization for torque production and minimizing conduction losses in the power transistors
Solution Approach 2:
The system optimizes power efficiency by dynamically changing electrical parameters including PWM duty cycles, switching frequencies, and current magnitudes. By adapting these parameters to actual operating conditions, the system achieves high torque output efficiency while minimizing energy losses in the power electronic components
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach eliminates the need for costly position sensors, enhances the motor's efficiency and reliability by enabling precise torque control and self-learning capabilities, and ensures safe operation by limiting kinetic energy during power failures.
Implementation Method 1
A torque generated by such an electromagnetic rotating field is almost constant irrespective of the position of the rotor
Implementation Method 2
an annular permanent magnet rotor with 2m permanent magnet segments of alternating polarity (N, S)
Data Source
AI summary
A DC-motor (46) actuates a highly-reduced reduction gear of an actuating drive for a flap or valve in order to regulate a gas or liquid volume flow, particularly for heating/ventilation/climatization, or fire or room protection. Current flow in the stator coils (A, B, C) is commutated in a program-controlled manner without integrated position sensors. Algorithms enable counting rotations of rotor (54) of the DC-motor (46). Problems related to the principle of motor rotation speed at low rpm are prevented. The DC-motor (46) includes a stator (44) having three stator coils (A, B, C) which extend over 3n stator poles (52), and an annular-shaped permanent magnet rotor (54) having 2m permanent magnet segments with alternating polarity (N, S), a coaxial cup-shaped external rotor (110) and a coaxial drive shaft (108), whereby n and m are whole multiplication factor numbers (1, 2, 3, 4) and are different from each other. Drive shaft (112) comprises, preferably, a spring (120) for the automatic return in case of current interruption.